Insect pests


Following is a list of the most common pests that can be found in your garden and some ways to control them. It does not list every pest or every way to control them. Further information can be found in the Ortho Problem Solver, or try the Master Gardeners great new Garden Hotline at (908)654-9852.

Adelgid- This has become a devastating pest on our native hemlocks. With no natural predators, northeast hemlock forests are being destroyed. Trees take on a silvery yellow color and closer inspection shows a cottony white insect on the underside of the needles. These sucking insects thrive on a well fed tree so resist the temptation to fertilize these weak looking trees. Best controls seem to be dormant or horticultural oil in early and late season and Orthene, Isotox, Diazinon, or malathion in May- June. Two or more applications are usually needed. Best control, unfortunately, AVOID USING HEMLOCKS.

Aphids- There are many types of aphids and they can strike a large variety of plants. They can be green, black, red, or other colors. They build up large populations on tender new growth in spring or throughout the season. Often these populations seem to build up and then disappear on their own, possibly due to natural predators. They can distort new growth and weaken plants so control may be necessary. A number of sprays can be used and plants recover quickly.

Bagworm- This pest forms a protective cover or bag over itself using the plants leaves and material. It likes arborvitae and other evergreens, chewing on the needles and leaves and stripping the tree. If you pull the bag apart, you will see the caterpillar inside. Because of the covering, a systemic spray like Isotox or Orthene is needed.

Beetles- There are lots of different beetles which can be bothersome throughout the season. Best known would be the Japanese beetle, which feeds on roses and many other flowers and plants. Adult beetle damage, while making the plants flowers and leaves unsightly, usually will not kill the plant. Many sprays are available.

Caterpillars- The juvenile stage of butterflies and moth are heavy feeders of some plants flowers and leaves. Damage does not usually kill the plant. Hand picking can help or if numbers are overwhelming, many sprays are available. BT or Neem are two organic sprays which are quite effective on these.

Cutworm- This caterpillar like monster stays in the soil and feeds on the stems of flowers and vegetables right at the soil line. In the morning, plants are found lying on their side with a clean cut at the base. Diatomaceous earth helps, as will making paper collars to protect young plants

Four-lined Plant Bug- Annoying, but seldom health threatening, this small green with reddish line quick moving bug leaves brown dots on the new leaves of a wide variety of plants, such as basil, forsythia, mints, and mums. Many sprays will work, but if you are quick, hand picking will work as there is usually just a few bugs doing what seems like a great deal of damage.

Lacebug- Pieris and azaleas seem to be sickly and yellow. Closer inspection may show a spotted or stippled look to the leaves and a black dotting on the underside or even the small lacy winged bug which sucks the strength from the plants. Orthene or malathion are pretty effective.

Scales- The most visible stage of this insect is a shell-like form which sticks to stems and leaves. Some forms, like Euyonmous scale or Cottony scale have white cottony stuff covering them. Because of the protective shell, a systemic may be needed. Best approach may be to use a horticultural oil early and late in the season and another pesticide in May-June depending on the scale.

Slugs- These slimy critters feed heavily on many flowers and herbs. They have been terrible during the last few years because of the mild winters and wet springs. At night they feed on flowers and hide during the day in mulch and among plants. Start fighting them as soon as damage is seen. Hand picking (Yuck!) and putting out traps of beer in saucers helps but a slug bait, such as Bugeta, is more effective.

Spider Mite- Plants, such as Alberta Spruce, marigolds, houseplants, or many others, seem to yellow and weaken, esp. during hotter weather. New growth may be curled. Clip a piece of the new growth and tap over a piece of white paper. If present, you should be able these barely visible mites moving around. Many times, webbing can be seen between needles and leaves. Malathion, Orthene, Diazinon, and other sprays can be effective.

Thrips- These tiny little terrors hide and feed on blooms, buds, and other growth, distorting growth and spreading disease. A systemic is needed to get to them and follow-up sprays should be done.

Weevil- Root weevil is the worst pest on many shrubs. Watch for notching and pieces missing on leaves. Watch for the adult weevil, a small black beetle, feeding at night. The grub, which is feeds on roots and stem of plants, is even more destructive. Spray plant and soil underneath with Orthene or Isotox beginning as new growth starts in spring and repeat 3 times a month apart.

Whitefly- These are more annoying than damaging. Whitefly numbers builds up quickly and plants seem to erupt with clouds of them when brushed. Outside, natural predators and wind seems to keep their levels in check. Inside, pyrethrum can help. During nice weather, try getting the plants outside. You may be able to use a more potent spray and just the action of the wind does help.

Read the whole label of any pesticide you use. Double check the rate used. Be sure it can be used on the plant you are spraying and for the pest that you are battling. Spray on days that are not windy or when rain is not expected within 24 hours. Donít spray plants that are stressed by heat or dry weather. Use sensible cover- no bare feet, t-shirts, etc.


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